This invention relates to an access door to be installed on a selected ceiling slab, side wall or shaft of a building to allow workers access to piping, wiring and air duct systems and other facilities installed between ceiling and floor slabs, between side walls and or within shafts for inspection and/or repair thereof.
As will be easily understood and precisely grasped from the description given hereinafter, in brief, in the access door of the present invention, an inner square frame is disposed within and pivotally connected to the frame opening defined by an outer square frame disposed within an opening formed at an installation area such as a building ceiling or side wall for movement between open and closed positions, the inner frame comprises a joint finishing flange at the peripheral edge of the frame member so as to conceal the peripheral edge of the outer frame on the outer surface of the installation area when the inner square frame is in its closed position, a pair of link hinge means is provided on each of two selected opposing sides of the outer frame and includes means for pivotally connecting the inner square frame to outer square frame, the inner square frame is rotatable with respect to the outer frame with the center of rotation of the inner frame positioned adjacent to one of the two other sides of the outer square frame to provide a single joint finishing structure whereby when the inner frame is opened the access door is opened at an increased area, the applicability of the access door to various ceiling is enhanced and the versatility of the access door is increased.
And in the access door of the present invention, the outer square frame comprises an assembly of two frame members each defining one half of the frame opening to be defined by the outer frame and connected together by butt joint to thereby increase the rigidity of the outer frame and more particularly, the rigidity of the outer frame for air tight and smooth opening and closing movement of the inner square frame.
Furthermore, in the access door of the present invention, a trim means positioned between an opening formed in a building ceiling, side wall or the installation area for the access door and the outer square frame to increase the application range of the access door whereby the access door can be suitably applied to building ceiling constructed by the so-called exposed, concealed and dry wall processes.
One of the conventional access doors such as a ceiling access door, for example, comprises an outer frame fitted in an opening in a building ceiling and secured to the ceiling by means of fasteners, an inner frame positioned within the frame opening defined by the outer frame and rotatably connected to the outer frame by means of a shaft and bearings and a cover plate or door attached to the inner frame to close the frame opening defined by the inner frame. When the cover is in its closed position, the cover is locked to the outer frame by means of a cremone lock and allowed to rotate about the shaft and bearings downwardly from the closed position to the open position.
In the conventional ceiling access door having the components constructed and arranged in the manner mentioned above, the outer frame is usually formed by cutting a cold rolled shaped steel or aluminum alloy blank of indefinite length into four frame members of a predetermined length and connecting the frame members together by use of corner pieces or alternatively, by roll formed steel or aluminum alloy into shaped blanks of indefinite length with grooves, cutting the blank into four frame members each having grooves at the opposite ends of a predetermined length, connecting the four frame members together in a square formation by butt joint and driving corner pieces into the grooves at the ends of the frame members associated with each other to provide an assembly. Alternatively, a frame member blank is cut into four frame members of a predetermined length, the four frame members are connected together by butt joint and spot welded together at the corners defined by the abutting frame members.
Since the outer frame in the conventional access door is formed by any one of the above-mentioned three types of processes, the assembling operation efficiency of the outer frame is low, the frame members are not always precisely butt jointed resulting in a non-uniform product and furthermore, since the outer frame has a number of connected points it is difficult to provide an air-tight outer frame having sufficient rigidity.
And since the inner frame having the cover attached thereto is rotatably or pivotally connected to the outer frame through the shaft and bearings when the access door is opened, the opening area of the access door or the open area of the frame opening defined by the outer frame is subjected to limitation and the area of the outer and inner frames appearing on the ceiling surface is a double-joint finishing structure instead of a single-joint finishing structure. Furthermore, the conventional access door had to be produced to be suitably employed in a particular ceiling structure or made to order and lacked in versatility.